sched: revert recent removal of set_curr_task()

Revert removal of set_curr_task.
Use put_prev_task/set_curr_task when changing groups/policies

Signed-off-by: Srivatsa Vaddagiri < vatsa@linux.vnet.ibm.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index 3503fb2..5ebf829 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -50,6 +50,10 @@
 {
 }
 
+static void set_curr_task_idle(struct rq *rq)
+{
+}
+
 /*
  * Simple, special scheduling class for the per-CPU idle tasks:
  */
@@ -66,6 +70,7 @@
 
 	.load_balance		= load_balance_idle,
 
+	.set_curr_task          = set_curr_task_idle,
 	.task_tick		= task_tick_idle,
 	/* no .task_new for idle tasks */
 };